Toward a more accurate silicon stereochemistry: An electron diffraction study of the molecular structure of tetramethylsilane

The present electron diffraction study of the molecular structure of tetram ethylsilane, augmented with theoretical calculations, answers the need for accurate and detailed information on the most fundamental molecules contain ing silicon. The Si-C bond length is r(g) = 1.877 +/- 0.004 Angstrom, in pe rfect agreement with a previous study (Beagley, B.; Monaghan, J. J.; Hewitt , T. G. J. Mol. Struct. 1971, 8, 401). The C-H bond length is r(g) = 1.110 +/- 0.003 Angstrom and the Si-C-H angle is 111.0 +/-0.2 degrees. The experi mental data are consistent with a model of Td symmetry and staggered methyl conformation. The barrier to methyl rotation is estimated to be 5.7 +/- 2. 0 kJ mol(-1) on the basis of the experimentally observed average torsion of the methyl groups.